Carton with improved folding

ABSTRACT

The present invention provides a carton ( 100 ) made of paperboard having flaps ( 101, 105 ), the carton ( 100 ) comprising, at least one score ( 102 ) along a crease line ( 103 ) of at least one flap ( 101, 105 ), wherein the score ( 102 ) is 25% to 85% of thickness of the paperboard and 5% to 70% of length of the crease line ( 103 ). The invention also provides a method of securing flaps ( 101, 105 ) of the carton ( 100 ).

FIELD OF THE INVENTION

The present invention relates to carton with flaps. Most particularly the present invention relates to paperboard carton having flaps with improved folding and a method of securing the flaps of the carton.

BACKGROUND OF THE INVENTION

Cartons find varied uses in the packaging industry. Even though the packaging industry has evolved and found a variety of other materials for packaging such as plastics, metals, alloys, glass, wood etc. However, still paper finds wide use because it is low cost, ability to hold its shape, and ease of being decorated.

Paper can also be laminated to increase strength or provide barrier properties. The materials used can be gloss or matt finished or embossed. Other materials can be laminated onto paperboard e.g. foil or plastics. Packaging produced using paper and board includes cartons, labels, leaflets, tubes, corrugated cases, rigid boxes and pulp packs.

Therefore, paperboard is still the material of choice for many packaging applications for the unique features and advantages that it offers.

By virtue of its nature, every material has got some stiffness value attached to it. With reference to board word “stiffness” relates to the board strength for cartons to withstand the external pressure/impact. The general norm for boards used for cartons is higher the board stiffness better strength or rigidity of the formed carton. To prevent moisture ingress inside or to increase the pack aesthetics, board is generally laminated on one side or on both sides with plastic film. It is well established that film lamination or coating increases the board stiffness.

Higher board stiffness results in increase in crease recovery force. Crease recovery force is the recoil force with which the carton flaps try to regain their position when the external force is released. Higher crease recovery force sometimes results in open glued end cartons after online packing operation itself or during transit due to tremendous recovery force results in cartons opening at depots causing depot freeze.

Patent No. U.S. Pat. No. 4,447,479 (Plastona (John Waddington) Ltd., 1984) relates to plastic sheet material, and in particular concerns the production of a plastic sheet material and discloses that a half-cut is provided in the sheet material for improving the dead fold characteristics of the sheet.

DE671344A discloses a method for preparing blanks for folding cartons and similar work pieces, wherein at the bending edges, in the same direction with them, a larger number of cuts is provided, which are arranged with spacing from each other in a row.

However, there are critical differences between paperboard materials and plastics which make the extrapolation of the disclosure of U.S. Pat. No. 4,447,479 not suited for implementation of this technology to paperboard on a factory scale without further inventive efforts. Paperboard material, unlike plastics, is neither impact resistant nor heat sealable and tends to be irreparably damaged once a cut is arbitrarily made. There is a critical balance which has to be maintained between a cut made to improve the dead fold characteristics of paperboard and at the same time retaining the structure and rigidity of the carton to prevent it from making it susceptible to damage.

Therefore there is a need to have a method for improving dead fold characteristics of a paper board carton without altering the strength of its structure.

SUMMARY OF THE INVENTION

The present invention relates to paperboard cartons having flaps with reduced crease recovery force and method for manufacturing the same.

First aspect of the present invention provides a carton made of paperboard, having flaps, the carton comprising, at least one score along a crease line of at least one flap, wherein the score is 25% to 85% of thickness of the paperboard and 5% to 70% of length of the crease line.

Second aspect of the present invention provides a method of securing flaps of a carton made of paperboard, the method comprising, making at least one score along a crease line of at least one flap, wherein the score is 25% to 85% of thickness of the paperboard, and is 5% to 70% of length of the crease line.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a paperboard carton with improved folding characteristics. The invention relates to carton with flaps where there are scores along the crease lines of the flaps.

Throughout the description of the present invention the term score means a scratch or an incision as it is ordinarily understood by the general meaning of the term. The term however is not meant to include perforations either singular or in series.

Throughout the description of the invention the score percentage of the length of crease line is the percent of score that covers the crease line whether it is single or plurality of scores.

The present invention provides a carton made of paperboard, having flaps, the carton comprising, at least one score along a crease line of at least one flap, wherein the score is 25% to 85% of thickness of the paperboard and 5% to 70% of length of the crease line.

In a preferred embodiment, the crease line has a single score and score preferably is 5% to 35% of the length of crease line and more preferably 10% to 25% of the length of crease line.

Another embodiment of the present invention provides a paperboard carton having plurality of scores.

In another preferred embodiment, the crease line has plurality of scores and the sum of scores preferably is 20 to 60% of the length of crease line and more preferably 30% to 55% of the length of crease line and most preferably 50% of the length of crease line.

One embodiment of the present invention provides a paperboard carton wherein preferably the score is 30% to 70% of thickness of the paperboard. More preferably the score is 50% to 60% of thickness of the paperboard and most preferably 50% deep with respect to thickness of the paperboard.

Another embodiment of the present invention provides a paperboard carton wherein preferably the score is 20% to 65% of length of the crease line. More preferably the score is 40% to 60% of length of the crease line and most preferably the score is 50% of length of the crease line.

A preferred embodiment of the present invention provides a carton having at least two scores on the crease line of each top and bottom flap. In a further preferred embodiment the side flaps have at least one score.

In another embodiment the top and bottom flaps are mutually superimposed and glued to form the carton.

Another embodiment of the present invention provides a carton wherein score is at crease line of each flap in the carton.

Another embodiment provides a blank for making the carton of the present invention. The blank for making the paperboard carton has scores at the predetermined crease lines of the flaps.

In another embodiment of the present invention, the paperboard has a plastic component laminated on it.

The present invention also provides a method of securing flaps of a carton made of paperboard, the method comprising, making at least one score along a crease line of at least one flap, wherein the score is 25% to 85% of thickness of the paperboard, and is 5% to 70% of length of the crease line.

One embodiment of the present invention provides a method of securing flaps of a folding paperboard carton wherein, the score is 30% to 70% of the thickness of the paperboard and more preferably the score is 50% to 60% of the thickness of the paperboard and most preferably 50% of the thickness of the paperboard.

In another embodiment of the present invention the score is 20% to 65% of length of the crease line and more preferably the score is 40% to 60% of length of the crease line and most preferably the score is 50% of length of the crease line.

Crease Recovery

Crease recovery is determined by the decrease in resistance offered by creased board after it is folded 90° at the crease measuring the recovery force after 15 seconds. Board Stiffness is determined by bending a 50mm length of board through a 15° angle.

Crease Recovery Force

It is the force required to hold a scored sample folded at 90 degrees for 15 seconds. The measurement is made at the end of this period of 15 seconds. The result will be the spring-back force (also called the crease recovery).

Cartons must have appropriate & Consistent creasing to ensure efficient performance on high-speed packing machines.

In modern high-speed packaging machines it is very important to have the creases in boards correct and uniform. The value of crease stiffness is technically important in the folding of carton blanks during their erection and closure, whether this is by hand or by mechanical means. The crease recovery (spring back) can result in forces, which distort the erected carton or cause stresses to be applied to closures, which reduce their effectiveness. Crease recovery is determined by the decrease in resistance offered by creased board after it is folded 90° at the crease measuring the recovery force at 15 seconds.

Material

Papers and boards come in different weights and sizes. Paper is measured in grams per meter squared (gsm), this refers to the weight per square metre. Anything over 200 gsm is classed as board. Paperboard is a paper-based material that is generally thicker than paper. It is easy to cut and form and is both lightweight and strong, which makes it ideal for packaging. Examples of the use of paper and paperboard packaging are found in many places, such as supermarkets, traditional street markets, shops and departmental stores, as well as for mail order, fast food, dispensing machines, pharmacies, and in hospital, catering, military, educational, sport and leisure situations.

Paper and paperboard, in many packaging forms, meet the packaging needs because they have appearance and performance properties which enable them to be made into a wide range of packaging structures cost-effectively. They are printable, varnishable and can be laminated to other materials. They have physical properties which enable them to be made into flexible, semi-rigid and rigid packages by cutting, creasing, folding, forming, winding, gluing, etc. Paper and paperboard packaging is used over a wide temperature range, from frozen-food storage to the temperatures of boiling water and heating in microwave and conventional ovens (Handbook of Paper and Paperboard Packaging Technology, 2013).

GSM

Basis Weight, better known as GSM indicates thickness of paperboard, cardboard or like material. It signifies the weight or substance per unit area of the material and is usually expressed as the weight in grams per square metre (g/m2). Higher GSM implies thicker material which in turn implies more strength.

Carton Manufacturing

Carton manufacturing can be sheet fed or roll fed process. In sheet fed process, board sheets are considered for printing depending upon the number of up calculation basis final carton dimensions, and in roll fed process board in form of roll is considered.

Printing process most commonly used is offset however gravure is also used for some specific application. Post input selection, board is printed. Post printing layer of varnish is applied on top. Depending upon the type of varnish used Aqueous or UV, varnish application process may be one step or two step. Post varnish application on top, ideally printed board are cured for 24 36 hrs and then considered for punching, creasing and final manufacturing joint gluing.

Punching Creasing and Scoring

Creasing is provided on the carton surface as an impression for providing ease of folding of flaps from particular position. This step is done along with the punching operation. Punching and creasing are done as a one step process. Special fabricated dies are used along with the pneumatic pressure for making desired depth of creasing.

Carton punching, creasing & scoring is preferably done as a single step process. It is preferable to use a single die having different finish blades for producing punched creased and scoring profile on desired position.

In an embodiment of the present invention a pneumatic pressure of about 120 tons is preferred for the die on a board size of 1020×720 mm.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic representation of the paperboard carton of present invention with open flaps.

FIG. 2 is a schematic representation of the paperboard carton of present invention with closed flaps.

DETAILED DESCRIPTION OF DRAWINGS

FIG. 1 shows the carton (100) of the present invention having flaps (101—top and bottom; the bottom flap is not shown; 105—side flaps) both along the length and breadth of the opening of the carton. The figure shows scores (102) on the crease lines (103) of the flaps. A partially cut-away enlarged view of the crease line (103) of the flap (101; 105) shows that the scores (102) along the crease line (103) are less than the thickness (104) of the paperboard carton.

FIG. 2 shows a closed paperboard carton of the present invention with scores (102) depicted on the crease lines (103).

EXAMPLES

Technical benefits of the disclosed invention will now be explained further with the help of a non-limiting example.

Methodology

Example 1

Two types of paperboard cartons were taken for conducting experiments for testing the crease recovery force of the cartons of the present invention.

-   -   1) Carton I—350 GSM grey back board with 10 μm metalized         polyethylene terephthalate (MET-PET) lamination on the         paperboard on the outer side of carton.     -   2) Carton II—350 GSM white back board with 10 μm metalized         polyester (MET-PET) lamination on the paperboard on the outer         side of carton and 10 μm clear polyethylene terephthalate (PET)         lamination on the inner side of the carton.

Both boards were top printed using transparent inks and UV texture and spot varnish on the top. After the printing and varnish application board sheets are left for curing for 12-36 hours.

Post curing board was punched using special dies fabricated to make score profile on the creasing line in step operation. The score was around 50% deep. Plurality of scores along top and bottom flaps covered around 70% of the crease line and a single score on each of the side flaps covered around 33% of the crease line. Carton punching, creasing & scoring was done as a single step process. Single die having different finish blades were used for producing punched cartons, creasing and scoring profile on desired position. A pneumatic pressure of about 120 tons was used for the die on a board size of 1020×720 mm.

For the controls, a different die was used without a provision for scoring. Therefore for each type of carton the controls had no score across the crease line, whereas the experimental cartons had scores on two flaps on the left opening of the rectangular carton box (L1 and L2) and two flaps on the right opening of the rectangular carton box (R1 and R2).

Process of Performing Test:

Carton strips of required sample size are taken and mounted on the crease recovery tester (IDM instruments: Crease and Stiffness Tester, model C0039). While sample preparation it is important to keep in mind samples should contain the creasing area equidistant from both the edges.

Post mounting samples, an external force is applied for 15 sec and then removed. Due to the inherent property of regaining the original position post removal of external force, the crease gives a crease recovery force and measured in terms of gf (gram force) named at crease recovery force.

TABLE 1 Testing Crease recovery force of Cartons Without With score Carton Score/Control (gram Type Flap (gram force) force) Carton I L1 140.3 101 Carton I L1 135.5 89 Carton I L1 122.5 82.4 Carton I L2 138.1 93.5 Carton I L2 127.7 93.6 Carton I L2 115 93 Carton I R1 125.6 97.1 Carton I R1 121 86.6 Carton I R1 135 87.8 Carton I R2 125.7 96.3 Carton I R2 118.1 63.3 Carton I R2 123 88.1 Carton II L1 157.2 86.7 Carton II L1 161.1 94.2 Carton II L1 153.6 92.2 Carton II L2 161.1 87.0 Carton II L2 179.1 98.6 Carton II L2 165.4 85.1 Carton II R1 179.7 94.5 Carton II R1 196.7 89.3 Carton II R1 154.4 90.4 Carton II R2 165.2 88.9 Carton II R2 152.2 92.3 Carton II R2 150.6 99.5

The data in Table 1 shows that the trial carton having score profile on the creasing shows lesser crease recovery force values post removal of the external force vs. a carton on which there is scoring. 

1. A carton (100) made of paperboard, having flaps (101, 105), the carton (100) comprising, at least one score (102) along a crease line (103) of at least one flap (101, 105), wherein the score (102) is 25% to 85% of thickness (104) of the paperboard and 5% to 70% of length of the crease line (103).
 2. A carton as claimed in claim 1, wherein the score (102) is 30% to 70% of the thickness (104) of the paperboard.
 3. A carton as claimed in claim 1, wherein the score (102) is 50% to 60% of the thickness (104) of the paperboard.
 4. A carton as claimed in claim 1, wherein the score (102) is 20% to 65% of the length of the crease line (103).
 5. A carton as claimed in claim 1, wherein the score (102) is 40% to 60% of the length of the crease line (103).
 6. A carton as claimed claim 1, wherein the score (102) is at the crease line (103) of each flap (101, 105).
 7. A blank for making the carton (100) as claimed in claim
 1. 8. A method of securing flaps (101, 105) of a carton (100) made of paperboard, the method comprising, making at least one score (102) along a crease line (103) of at least one flap (101, 105), wherein the score (102) is 25% to 85% of thickness (104) of the paperboard, and is 5% to 70% of length of the crease line (103).
 9. A method as claimed in claim 8, wherein the score is 30% to 70% of the thickness of the paperboard.
 10. A method as claimed in claim 8, wherein the score is 50% to 60% of the thickness (104) of the paperboard.
 11. A method as claimed in claim 8, wherein the score is 20% to 65% of length of the crease line (103).
 12. A method as claimed in claim 8, wherein the score is 40% to 60% of length of the crease line (103). 